Method and apparatus for manufacturing packaging bags, and bags obtained thereby

ABSTRACT

The present invention relates to a method of manufacturing packaging bags having lateral bellows, the method being characterized by the fact that it comprises the steps consisting in: forming respective cutouts ( 150, 160 ) in each of the two lateral, bellows-forming zones of a packaging bag sheet ( 100 ) so that the bag has only two thicknesses superposed at the mouth of said bellows, at least over a portion of its width; and heat-sealing ( 184, 186 ) the adjacent edges of the sheet to the peripheries of the cutouts ( 150, 160 ) to close the bag. The invention also provides apparatus for implementing the method and bags obtained thereby.

[0001] The present invention relates to the field of bags for packaging.

[0002] Numerous packaging bags and numerous systems for manufacturingthem have already been proposed.

[0003] For bags of small thickness, i.e. that are generally flat in thefilled state, known means generally give satisfaction. Under suchcircumstances, the bags are generally formed using two plane sheets thatare bonded together along three sides and that are provided with closuremeans, e.g. complementary male/female strips, at the mouth of a bag.

[0004] In contrast, until now, making bags that are intended to receivecontents that are thick, has turned out not to be entirely satisfactory,even though a large amount of research has been performed in this veryspecific field.

[0005] In particular, such bags often require lateral bellows which aredifficult to make.

[0006] Accompanying FIG. 1 shows, diagrammatically, a known techniquefor making bags with lateral bellows by inserting pre-formed bellows 10between two sheets 12 and 14 that constitute two main faces of the bags,with the bellows being inserted at 90° to the travel direction S of saidsheets. Said sheets 12 and 14 are provided with longitudinal male/femaleclosure strips 13 and 15. The bellows 10 are preferably of varyingwidth, increasing away from the closure strips 13 and 15 so as to enablethe bags to be inflated. That known technique does indeed make itpossible to make packaging bags having lateral bellows. Nevertheless, itturns out to be quite complex. In particular, the need to insert thebellows 10 at 90° to the travel direction of the sheets 12 and 14 doesnot enable high manufacturing throughputs to be obtained, and requiresinsertion of the bellows 10 to be adequately synchronized with thetravel of the sheets 12 and 14.

[0007] Document FR-A-2 686 063 describes another technique ofmanufacturing packaging bags with bellows that consist in preforming abag with lateral bellows, in splitting the bag over a portion of itslength along fold lines external to the bellows, in folding the flapsdefined in this way back over the outside of the bag, in placing theclosure strips on said flaps, in reforming the bag, and in bonding theclosure strips to said flaps that have been put into place.Unfortunately, because of its complexity, that technique does not givefull satisfaction.

[0008] The Applicant has also described various alternative solutionsfor manufacturing packaging bags with lateral bellows in French patentapplication No. 96 02389 filed on Feb. 27, 1996.

[0009] The present invention now seeks to improve known means formanufacturing packaging bags having lateral bellows.

[0010] This object is achieved in the context of the present inventionby a method of manufacturing packaging bags characterized by the factthat it comprises the steps consisting in:

[0011] forming respective cutouts in each of the two lateral,bellows-forming zones of a packaging bag sheet so that the bag has onlytwo thicknesses superposed at the mouth of said bellows, at least over aportion of its width; and

[0012] heat-sealing the adjacent edges of the sheet to the peripheriesof the cutouts to close the bag.

[0013] The present invention also provides apparatus for implementingthe method, and bags obtained thereby.

[0014] Other characteristics, objects, and advantages of the inventionwill appear on reading the following detailed description and on lookingat the accompanying drawings, given by way of non-limiting example andin which:

[0015]FIG. 1, described above, is a diagram showing a conventionaltechnique of manufacturing packaging bags having lateral bellows;

[0016]FIG. 2 shows a first step of a method of the present inventionconsisting in forming two Z-folds in a film;

[0017]FIG. 3 is a cross-section view through the same film;

[0018]FIG. 4 is a view similar to FIG. 2 and shows the portion of filmthat is removed to form cutouts;

[0019]FIG. 5 shows the same film as provided with cutouts, when spreadout flat;

[0020]FIG. 5bis is a similar flat view of a variant film of the presentinvention that is provided with cutouts; and

[0021] FIGS. 6 to 9 show four successive steps of the method of thepresent invention for forming bags.

[0022] In FIG. 2, there can be seen a film 100 provided with two Z-folds110 and 120 that are parallel to the longitudinal direction D of thefilm 100.

[0023] The two Z-folds 110 and 120 can be formed by any appropriatemeans.

[0024] Each of them is preferably formed by means of two blades 200 &202 or 200 & 204 that are superposed with partial overlap, as shown inFIG. 3, so as to form a baffle into which the film 100 is engaged.

[0025] The folds 110 and 120 are designed to form the lateral bellows ofthe bag once it has been completed.

[0026] After the folds 110 and 120 have been made, the film as shown inFIG. 2 has a plane main face 130 that is to form a main face of the bagafter it has been completed. On its longitudinal edges, this main face130 is extended on either side by first longitudinal flaps 112 and 122which are themselves extended by second longitudinal flaps 114 and 124.The flaps 112 and 114 form the fold 110. The flaps 112 and 114 form thefold 120. The flaps 112 and 122 are connected to the main face 130 viafold lines 111 and 121. The flaps 112 and 122 are folded towards themiddle of the face 130 from the fold lines 111 and 121 so that theyunderlie the main face 130. The flaps 114 and 124 are connected to theflaps 112 and 122 via fold lines 113 and 123. The flaps 114 and 124extend outwards from the fold lines 113 and 123. The flaps 114 and 124are also of the same length as the flaps 112 and 122 so as to underliethem respectively, being immediately beneath them. Finally, each of theflaps 114 and 124 is extended outwards by auxiliary segments 140 and142. These auxiliary segments 140 and 142 are designed, in combination,to form the second main face of the bags. As shown in FIG. 2, the twosegments 140 and 142 are preferably of identical width. Nevertheless,this condition is not essential. What is essential is that the segments140 and 142 possess a total width that is slightly greater than thewidth of the face 130 so as to form the second face of the bags afterthey have been folded about their outer longitudinal free edges, asexplained below with reference to FIG. 8.

[0027] After the step of forming the folds 110 and 120 as shown in FIG.2, the flaps 114 and 124 are substantially coplanar with the segments140 and 142. The flaps 114 and 124 are connected to the segments 140 and142 via lines 115 and 125.

[0028] As mentioned above, according to an essential characteristic ofthe present invention, the method of forming a bag includes a step ofcutting out pairs of cutouts 150 and 160 at regular intervals in each ofthe zones that is to form a lateral bellows.

[0029] The areas of material removed to form these cutouts 150 and 160are shaded in FIG. 4.

[0030] The cutouts 150 and 160 are shown in the deployed state in FIG.5.

[0031] Finally, the cutouts 150 and 160 are shown in their realconfiguration within the folds 110 and 120 in FIG. 6.

[0032] The cutouts 150 and 160 can be formed in the film 100 beforemaking the folds 110 and 120. Under such circumstances, their initialshape is as shown in FIG. 5.

[0033] Nevertheless, it is preferable for the cutouts 150 and 160 to beformed after the folds 110 and 120 have been made. The cutouts 150 and160 can be made in the film 100 by any appropriate means. The cutouts150 and 160 are preferably made using the blade 200 as an anvil thatco-operates with a cutting-out punch so as to leave the face 130 of thefilm intact.

[0034] The shapes of the cutouts 150 and 160 can vary in numerous ways.

[0035] The cutouts 150 and 160 preferably extend between the lines 111and 115 on one side and the lines 121 and 125 on the other side, asshown in FIG. 5. Nevertheless, in a variant, as shown in FIG. 5bis, thecutouts 150 and 160 can be formed so as to be set back from theabove-mentioned lines 111 & 115 and 121 & 125, as shown in FIG. 5bis.

[0036] More precisely, and as shown in the accompanying figures, each ofthe cutouts 150 and 160 is defined by two longitudinal edges 152 & 154and 162 & 164, and by two transverse edges 156 & 158 and 166 & 168.

[0037] The longitudinal edges 152 & 154 and 162 & 164 are rectilinearand coincide respectively with the lines 111, 115, 121, and 125 in FIG.5, which lines themselves constitute the final outer generator lines ofthe lateral bellows. In the folded state as shown in FIG. 6, the pairsof edges 152 & 154 or 162 & 164 are superposed.

[0038] The transverse edges 156 and 166 that are closer to the mouth ofa bag are preferably rectilinear, extending transversely relative to thelongitudinal direction D of the film 100.

[0039] The second transverse edges 158 and 168 that are closer to thebottom of a bag are preferably not rectilinear, being concave towardsthe mouth of the bag. More precisely, the second transverse edges 158and 168 are preferably in the form of a dihedral made up of tworectilinear segments 158 a & 158 b or 168 a & 168 b. The above-mentionedpairs of segments 158 a & 158 b and 168 a & 168 b constitutingrespective second transverse edges 158 and 168 are preferably identicalin length. They extend respectively over the flaps 112 & 114 and 122 &124. In this way, the segments 158 a & 158 b and 168 a & 168 b intersecton the middle fold lines 113 and 123.

[0040] As a non-limiting example, the segments 158 a & 158 b and 168 a &168 b are inclined by about 15° relative to a line extendingtransversely to the longitudinal direction D, such that the dihedralangle formed between the pairs of segments 158 a & 158 b and 168 a & 168b is about 150°.

[0041] The generally plane film 100 together with its two Z-folds 110and 120 and provided with its two cutouts 150 and 160 as shown in FIGS.5 and 5bis is preferably fed directly to a conventional form, fill, andseal machine for making bags.

[0042] Such machines are often referred to as “FFS” machines, from theinitials of the term “form, fill, and seal”.

[0043] Numerous machines of this type have already been proposed.

[0044] Most such machines have: a forming throat which has an inputreceiving the film in the flat state and which has an output deliveringthe film shaped into a tube; a filling chute which opens out into theforming throat and consequently into said tube; longitudinalheat-sealing means for closing the tube longitudinally; and meanssuitable for acting sequentially to generate a first transverse line ofheat-sealing before substance is inserted into the tube via the fillingchute, and then a second transverse line of heat-sealing once thesubstance has been inserted into the tube, so as to close the bag aroundthe substance.

[0045] The general structure of such machines is well known to theperson skilled in the art, so the structure is not described in detailbelow.

[0046] It will be observed that in the context of the present invention,it is preferable for complementary male/female closure strips 170 to bedeposited on the film 100 in the vicinity of the mouth zone of a bagtransversely to the longitudinal direction D, and prior to the film 100being brought to the forming throat of the FFS machine, as shown in FIG.7.

[0047] Still more precisely, closure strips 170 are placed against themain face 130 facing the cutouts 150 and 160, i.e. between thetransverse edges 156 and 158 at one end and 166 and 168 at the other.

[0048] The closure strips 170 are preferably of a length that is equalto the width of the main face 130, i.e. the distance between the foldlines 111 and 121.

[0049] After being placed on the film 100, the strips 170 are secured inposition on the film 100 by any appropriate means. Preferably, afterthey have been put into place, the strips 170 are initially fixed to thefilm 100 solely via their ends using a spot heat-sealing technique. Thestrips 170 are subsequently fixed to the main faces of the bag over thefull length of their inside faces, preferably when making the transverselines of heat-sealing in the manner described below with reference toFIG. 9. When the strips 170 are secured by spot heat-sealing at theirends, the lateral edges of the bag facing the folds 110, 120 can also besecured by spot heat-sealing at the zones where the transverse lines ofheat-sealing shown in FIG. 9 will subsequently be made for holding theabove-mentioned folds together and preventing them from deforming as thefilm 100 moves on.

[0050] Nevertheless, in a variant, at least one of the strips 170 may beheat-sealed to the film 100 along its entire length as soon as it is putinto place.

[0051] The above-mentioned means for spot heat-sealing are preferablyadjustable along the length of the film 100 so as to make it possiblefor them to be adjusted accurately relative to the desired length forthe bags and to the zones that will subsequently correspond to thetransverse lines of heat-sealing.

[0052] Naturally, it is also necessary to synchronize carefully theinstant at which said spot heat-sealing means are operated relative tothe travel of the film 100, since the instants at which said spotheat-sealing means operate determine both the locations of thecorresponding heat-sealing zones and the pitch of said zones.

[0053] By fixing the closure strips 170 via their ends, and possiblyalso by fixing the folds 110 and 120 by spot heat-sealing, subsequenttravel of the film 100 is made easier and it is also easier subsequentlyto perform the heat-sealing as shown in FIG. 9, particularly because ofthe resulting crushing of the ends of the strips 170.

[0054] The means for making the above-mentioned spots of heat-sealingcan be generally like the means described in document FR-A-2 638 419.

[0055] In a variant, the closure strips 170 are fixed, and the folds 110and 120 are held temporarily by spots that are not made by heat-sealing,but are made by any equivalent means, such as by static discharge or byspots of adhesive.

[0056] The means designed for depositing the closure strips 170 on thefilm 100 so that they extend transversely to the longitudinal directionD of the film 100 can be implemented in numerous ways.

[0057] By way of non-limiting examples, these means may be like themeans described in the following documents: U.S. Pat. No. 4,617,683,U.S. Pat. No. 4,655,862, U.S. Pat. No. 4,666,536, U.S. Pat. No.4,701,361, U.S. Pat. No. 4,709,398, U.S. Pat. No. 4,878,987, U.S. Pat.No. 4,844,759, U.S. Pat. No. 4,929,225, U.S. Pat. No. 4,909,017, andU.S. Pat. No. 5,111,643.

[0058] Once the folds 110 and 120 have been made and the closure strips170 have been put into place and secured, at least temporarily, the filmassembly 100 as shown in FIG. 7 is sent to the forming throat of an FFSmachine, as mentioned above.

[0059] Where appropriate, special means may be provided at the formingthroat to facilitate passage thereover, in particular of the folds 110,120. By way of example, complementary windows may be provided on theforming throat to receive the folds 110 and 120.

[0060] On leaving the forming throat, the film 100 is shaped into atubular state, as shown in FIG. 8. The outer free edges 141 and 143 ofthe segments 140 and 142 are then brought together and heat-sealed inconventional manner by the above-mentioned longitudinal heat-sealingmeans of the FFS machine.

[0061] The tubular film is then filled with its content via the fillingchute provided for this purpose.

[0062] The tubular film is then brought to face the heat-sealing meansprovided for making the lines of heat-sealing shown in FIG. 9.

[0063] The following are then preferably provided at these heat-sealingmeans:

[0064] two mutually parallel lines of heat-sealing 180 and 182; and

[0065] respective lines of heat-sealing 184 and 186 at the peripheriesof the cutouts 150 and 160.

[0066] One of the transverse lines of heat-sealing 180 coincides withthe transverse edges 156 and 166 of the cutouts. This transverse line ofheat-sealing 180 is designed to form the bottom of a bag. In the lateralbellows, it serves to connect together four thicknesses of film (the twomain faces and the lateral bellows) and between the bellows it connectstogether two thicknesses of film (corresponding to the main faces).

[0067] The other transverse line of heat-sealing 182 is made between thetransverse edges 156 & 158 and 166 & 168 of the cutouts. This transverseline of heat-sealing 182 is designed to form the mouth of a bag. Itinterconnects the two main faces.

[0068] Once the lines of heat-sealing 180 and 182 have been made, atransverse rectilinear line of cut 181 can be formed between them toseparate two adjacent bags.

[0069] The lines of heat-sealing 184 and 186 are respectively made up ofpairs of segments 184 a & 184 b and 186 a & 186 b respectively coveringthe longitudinal edges 152 & 154 and 162 & 164 and also the transverseedges 158 and 168 of the cutouts.

[0070] In this way, the lines of heat-sealing 184, 182, and 186intersect, thereby ensuring that the mouth of a bag is properly sealed.More precisely, the segments 184 a and 186 a connect together theoutside edges of the two main faces of the bag, while the segments 184 band 186 b connect together the edges 158 a & 158 b and the edges 168 a &168 b.

[0071] The method of the present invention has the fundamental advantageof limiting the lines of heat-sealing 184, 182, and 186 to twothicknesses of film, in particular where the closure strips 170 arefixed thereto, whereas most conventional methods need to performheat-sealing through four thicknesses of film at the lateral bellows.

[0072] Naturally, the present invention is not limited to the embodimentdescribed above, but extends to any variant coming within the spiritthereof.

[0073] For example, it is possible to make bags using a film of the typeshown in FIG. 7 having cutouts 150, 160 and closure strips 170, withoutapplying the film to a form, fill, and seal machine as mentioned above.The film can then be shaped to have a tubular state by any appropriateconventional means.

[0074] In the context of the present invention, the film 100 can bevaried in numerous ways. It is preferably constituted by a thermoplasticfilm. Nevertheless, the invention applies to any flexible film that canbe used for making a packaging bag.

[0075] Furthermore, the person skilled in the art will understand thatalthough, in the example shown in FIG. 5, the longitudinal edges 152,154, 162, and 164 of the cutouts 150 and 160 coincide with the foldlines 111, 115, 121, and 125, so that the lines of heat-sealing 184 aand 186 a are made on two thicknesses of film, when the longitudinaledges 152, 154, 162, 164 of the cutouts 150 and 160 are set back fromthe fold lines 111, 115, 121, and 125, then the lines of heat-sealing184 a and 186 a are made, at least in part, on four superposedthicknesses of film. The same applies for end portions of the transverselines of heat-sealing 180 and 182. The lines of heat-sealing 184 a and186 a may also be made at least in part so as to be set back from thefold lines 111, 115, 121, and 125, as shown in FIG. 9. The variantembodiment of the cutouts as shown in FIG. 5bis makes it possible toimprove the lateral sealing of the bags.

1. A method of manufacturing packaging bags having lateral bellows, themethod being characterized by the fact that it comprises the stepsconsisting in: forming respective cutouts (150, 160) in each of the twolateral, bellows-forming zones of a packaging bag sheet (100) so thatthe bag has only two thicknesses superposed at the mouth of saidbellows, at least over a portion of its width; and heat-sealing (184,186) the adjacent edges of the sheet to the peripheries of the cutouts(150, 160) to close the bag.
 2. A method according to claim 1 ,characterized by the fact that it includes the step consisting in makingtwo Z-folds (110, 120) parallel to the longitudinal direction (D) of thefilm (100).
 3. A method according to claim 2 , characterized by the factthat each of the Z-folds (110, 120) is formed by means of two blades(200, 202, 200, 204) that are partially superposed to overlap so as toform a baffle in which the film (100) is engaged.
 4. A method accordingto claim 2 or 3 , characterized by the fact that the cutouts (150, 160)are formed after the folds (110, 120) have been formed.
 5. A methodaccording to claim 2 or 3 , characterized by the fact that the cutouts(150, 160) are formed before the folds (110, 120) are formed.
 6. Amethod according to claim 3 , characterized by the fact that the cutouts(150 and 160) are formed using one of the fold-forming blades (200) asan anvil for a cutting-out punch, thereby leaving one of the faces (130)of the film untouched.
 7. A method according to any one of claims 2 to 6, characterized by the fact that after the folds (110, 120) have beenmade, the film has a plane main face (130) extended on either side atits longitudinal edges by first longitudinal flaps (112, 122), which arethemselves extended by second longitudinal flaps (114, 124), which arein turn extended outwards by auxiliary segments (140, 142).
 8. A methodaccording to any one of claims 1 to 7 , characterized by the fact thateach cutout (150, 160) is defined by two rectilinear longitudinal edges(152 & 154, 162 & 164) coinciding respectively with the outer generatorlines of the lateral bellows, a rectilinear transverse edge (156, 166)extending transversely to the longitudinal direction (D) of the film(100), and a second transverse edge (158, 168) that is not rectilinear,being concave towards the mouth of the bag.
 9. A method according to anyone of claims 1 to 7 , characterized by the fact that each cutout (150,160) is defined by two rectilinear longitudinal edges (152 & 154, 162 &164) situated respectively set back from the outer generator lines ofthe lateral bellows, a rectilinear transverse edge (156, 166) extendingtransversely to the longitudinal direction (D) of the film (100), and asecond transverse edge (158, 168) that is not rectilinear, being concavetowards the mouth of a bag.
 10. A method according to claim 8 or 9 ,characterized by the fact that the second transverse edge (158, 168) isconstituted by a dihedral made up of two rectilinear segments (158 a &158 b, and 168 a & 168 b).
 11. A method according to any one of claims 1to 10 , characterized by the fact that the film (100) provided with twoZ-folds (110, 120) and fitted with two cutouts (150, 160) is shapedusing a form, fill, and seal machine.
 12. A method according to claim 11, characterized by the fact that the form, fill, and seal machine has aforming throat whose input receives the film (100) in the flat state andwhose output delivers the film shaped into a tube, a filling chute whichopens out into the forming throat and consequently into said tube,longitudinal heat-sealing means for closing the tube longitudinally, andmeans suitable for sequentially generating transverse lines ofheat-sealing to close a bag.
 13. A method according to any one of claims1 to 12 , characterized by the fact that it further comprises the stepconsisting in placing complementary male/female closure strips (170) onthe film (100) in the mouth zone of a bag, transversely to thelongitudinal direction (D), facing the cutouts (150 and 160).
 14. Amethod according to claim 13 , characterized by the fact that the strips(170) are initially held in position on the film (100) by spotheat-sealing at their ends.
 15. A method according to claim 2 ,characterized by the fact that the folds (110, 120) are fixed by spotheat-sealing at the zones where the transverse lines of heat-sealing areto be formed.
 16. A method according to any one of claims 1 to 15 ,characterized by the fact that it comprises the steps consisting inmaking: two mutually parallel transverse lines of heat-sealing (180,182), one coinciding with a transverse edge (156, 166) of each cutout toform the bottom of a bag, the other being made between the transverseedges (156 & 158, 166 & 168) of the cutouts to form the mouth of a bag;and additional lines of heat-sealing (184, 186) each formed by twosegments (184 a & 184 b, 186 a & 186 b) respectively covering thelongitudinal edges (152 & 154, 162 & 164) of the cutouts and also thetransverse edges (158 and 168) of the cutouts.
 17. A method according toclaim 16 , characterized by the fact that a rectilinear line of cut(181) is formed between the two transverse lines of heat-sealing (156,166) to separate two adjacent bags.
 18. A machine for manufacturingpackaging bags having lateral bellows to implement the method accordingto any of claims 1 to 17 , the machine being characterized by the factthat it comprises: means suitable for forming respective cutouts (150,160) in each of the two zones forming lateral bellows of a sheet (100)for a packaging bag, such that the bag has only two superposedthicknesses at the mouths of said bellows, at least over a fraction ofits width; and means (184, 186) suitable for heat-sealing together theadjacent edges of the sheet at the peripheries of the cutouts (150, 160)to close the bag.
 19. A machine according to claim 18 , characterized bythe fact that it includes means for forming two Z-folds (110, 120)parallel to the longitudinal direction (D) of the film (100).
 20. Amachine according to claim 19 , characterized by the fact that itincludes two partially superposed blades (200, 202, 200, 204) thatoverlap to form a baffle into which the film (100) is engaged to formthe folds (110, 120).
 21. A machine according to claim 20 ,characterized by the fact that one of the fold-forming blades (200)forms an anvil for a cutting-out punch when making the cutouts (150,160), thereby leaving one of the faces (130) of the film intact.
 22. Amachine according to any one of claims 18 to 21 , characterized by thefact that each cutout (150, 160) is defined by two rectilinearlongitudinal edges (152 & 154, 162 & 164) respectively coinciding withthe outer generator lines of the lateral bellows, a rectilineartransverse edge (156, 166) extending transversely to the longitudinaldirection (D) of the film (100), and a second transverse edge (158, 168)that is not rectilinear, being concave towards the mouth of the bag. 23.A machine according to any one of claims 18 to 21 , characterized by thefact that each cutout (150, 160) is defined by two rectilinearlongitudinal edges (152 & 154, 162 & 164) situated so as to be set backrespectively from the outer generator lines of the lateral bellows, arectilinear transverse edge (156, 166) extending transversely to thelongitudinal direction (D) of the film (100), and a second transverseedge (158, 168) that is not rectilinear, being concave towards the mouthof the bag.
 24. A machine according to claim 22 or 23 , characterized bythe fact that the second transverse edge (158, 168) constitutes adihedral made up of two rectilinear segments (158 a & 158 b, 168 a & 168b).
 25. A machine according to any one of claims 18 to 24 ,characterized by the fact that it constitutes a form, fill, and sealmachine.
 26. A machine according to any one of claims 18 to 25 ,characterized by the fact that it includes a forming throat having aninlet that receives the film (100) in the plane state, and an outletthat delivers the film shaped into a tube, a filling chute which opensout into the forming throat and consequently into said tube,longitudinal heat-sealing means for closing the tube longitudinally, andmeans suitable for sequentially generating transverse lines ofheat-sealing to close a bag.
 27. A machine according to any one ofclaims 18 to 26 , characterized by the fact that it further comprisesmeans suitable for placing complementary male/female closure strips(170) on the film (100) in the mouth zone of a bag, the strips extendingtransversely to the longitudinal direction D and facing the cutouts (150and 160).
 28. A machine according to claim 27 , characterized by thefact that it includes means suitable for securing the strips (170)initially in position on the film (100) by spot heat-sealing at theirends.
 29. A machine according to any one of claims 18 to 28 ,characterized by the fact that it includes means suitable for fixing thefolds (110, 120) by spot heat-sealing in the zones that are subsequentlyto include the transverse lines of heat-sealing.
 30. A machine accordingto any one of claims 18 to 29 , characterized by the fact that itcomprises heat-sealing means suitable for making: two mutually paralleltransverse lines of heat-sealing (180, 182), one coinciding with atransverse edge (156, 166) of each cutout to form the bottom of a bag,the other being made between the transverse edges (156 & 158, 166 & 168)of the cutouts to form the mouth of a bag; and additional lines ofheat-sealing (184, 186) each made up of two segments (184 a & 184 b, 186a & 186 b) respectively covering the longitudinal edges (152 & 154 and162 & 164) and the transverse edges (158 and 168) of the cutouts.
 31. Amachine according to claim 30 , characterized by the fact that itcomprises means suitable for making a rectilinear line of cut (181)between the two transverse lines of heat-sealing (156, 166) to separatetwo adjacent bags.
 32. A packaging bag having lateral bellows made byimplementing the method according to any one of claims 1 to 17 .
 33. Abag according to claim 32 , characterized by the fact that it includesrespective cutouts (150, 160) in each of the two zones forming lateralbellows and a line of heat-sealing (184, 186) on the periphery of thecutouts (150, 160) to close the bag.